Various electronic training aids are known for enabling a dog trainer to immediately encourage or discourage various dog behaviors when the dog is off leash. Generally, the dog trainer carries a transmitter capable of sending radio signals to a receiver unit supported beneath a collar around the dog's neck enabling the dog trainer to apply stimuli to the free moving dog. The state-of-the-art is generally indicated by the present assignee's publication "Understanding Electronic Dog-Training" by Dr. Daniel F. Tortora, 1982, the assignee's Model Al-70, Model Al-80, and Model Al-90 remote trainer systems and MBL bark limiter manuals, assignee's U.S. Pat. Nos. 4,202,293 and 4,335,682, and U.S. Pat. No. 2,800,1004 (Cameron et al.).
The effectiveness of using the known animal training devices is limited by the portability and range of such systems, which in turn depend on the power output of the transmitter and the sensitivity of the receiver. Increasing the power output of the transmitter leads to rapid discharge of batteries in the portable transmitter devices, which is highly undesirable. Increasing the size or number of the transmitter batteries would be impractical, as the transmitter unit needs to be as small and light as possible. The transmitters of assignee's prior system produce only about 0.2 watts of output power, and hence do not cause a heavy power drain from the batteries. In applicant's prior devices, the receiver antenna is woven into the collar that supports the receiver unit about the dog's neck. The above-mentioned Cameron et al. patent shows a receiver unit supported on a dog's back by a harness. A rigid antenna is rigidly mounted on top of the receiver unit and extends upwardly from the back of the dog. This device is very impractical for long range purposes, as it is non-resonant and therefore very inefficient. Furthermore, as dogs often run under fences, through brush, etc., especially if distracted by a rabbit or a cat or the like, the rigid antenna of the Cameron et al. device is likely to be bent or damaged.
All electronic animal training devices of the type described above of which we are aware have a mean range limited to approximately one-quarter of a mile from the transmitter, under fairly ideal conditions. There usually are "gaps" or "radio dead spots" in the range of the prior devices, wherein the reliable range is substantially less than one-quarter of a mile. Such gaps in the one-quarter mile range can be caused by variations in the terrain, the orientation of the dog, orientation of the transmitter, and other factors. Therefore, as a practical matter, the prior electronic training devices are nearly 100% reliable only within one-eighth of a mile. Such "gaps" in the range of the unit can be very harmful to the progress of training an animal, because, as explained in the above Tri-Tronics publication by Dr. Tortora, effective training of a dog requires precise timing of the training stimuli. While in some instances the range of prior electronic dog training devices is satisfactory, in other instances, it is not. Competitors in this industry have expended considerable effort and investment in trying to devise a practical electronic dog training system that extends the range. Until now, such attempts have fallen short. One approach has been to increase transmitter power, but since the range is proportional to the square root of the power of the transmitter, this approach requires a large increase in the transmitter output power, greatly increasing battery power consumption therefore substantially increasing the size and weight of the transmitter unit by requiring larger battery packs. Other approaches have included attempts to attach stiff rod antennas to the receiver unit under the dog's collar so that the rod antenna extends along side the dog's neck and above the level of his back. Such attempts have been inadequate. First, to be efficient for dog training purposes, an antenna should be resonant at the operating frequency. Dogs frequently shake their heads vigorously, especially if they become wet, and a stiff rod antenna becomes very dangerous to persons and/or other dogs that might be nearby.
Furthermore, prior attempts at running a rod-type antenna past the dog's neck have not adequately increased the range, probably because of the close proximity to the dog's neck, which results in coupling some of the received energy directly to the dog's neck instead of to the receiver and also results in some detuning of the antenna circuit. Also, the presence of an antenna extending from a dog will alter the dog's judgment as to how close it can pass by an object without the antenna hitting the object. This can cause the dog to give excessive leeway when passing an object. Obviously, such a large rod antenna would be impractical.
The harness-supported receiver in the above-mentioned Cameron et al. reference is impractical because of the inconvenience of putting a harness on a strong, squirming dog and because of the likelihood of breaking off the antenna disclosed in that reference if the dog runs or crawls under a tree branch or a fence or the like in pursuit of a rabbit, cat, etc.
The state-of-the-art is such that those skilled in the art mostly have accepted the disadvantages inherent in using rigid wire or rod antennas as a means to increase the range of remote electronic dog training devices of the type referred to, and have accepted the fact that the high cost and/or high level of inconvenience associated with the various options for increasing the transmitter range, such as increasing transmitter power, increasing receiver sensitivity, extending stiff rod antennas from neck-mounted receivers, etc., are not practical in view of the benefits that can be attained thereby.